A method for writing a design to a material using an electron beam includes assigning a first dosage to a first polygonal shape. The first polygonal shape occupies a first virtual layer and includes a first set of pixels. The method also includes simulating a first write operation using the first polygonal shape to create the design, discerning an error in the simulated first write operation, and assigning a second dosage to a second polygonal shape to reduce the error. The second polygonal shape occupies a second virtual layer. The method further includes creating a data structure that includes the first and second polygonal shapes and saving the data structure to a non-transitory computer-readable medium.
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1. A method for writing a design to a material using an electron beam, the method comprising: assigning a first dosage to a first polygonal shape, the first polygonal shape occupying a first virtual layer and including a first set of pixels; performing a simulated first write operation of the first polygonal shape; discerning an error in the simulated first write operation; assigning a second dosage to a second polygonal shape to reduce the error, the second polygonal shape occupying a second virtual layer; creating a data structure that includes the first and second polygonal shapes; and saving the data structure to a non-transitory computer-readable medium.
A method for writing a design on a material using an electron beam involves these steps: First, assign a dosage value to a polygonal shape. This shape exists on a virtual layer and consists of a set of pixels. Then, simulate writing with that polygonal shape. Detect any errors that occur during this simulated writing process. To correct those errors, assign another dosage value to another polygonal shape, located on a second virtual layer. Combine these shapes and dosage values into a data structure, and save this data structure onto a computer-readable storage medium.
2. The method of claim 1 , in which creating the data structure comprises: merging the first virtual layer and the second virtual layer by adding the first dosage and the second dosage in an overlap area of the first and second polygonal shapes.
Building upon the method for electron beam writing and error correction, the process of creating the data structure involves merging the virtual layers. This merging is accomplished by adding the dosage values from both polygonal shapes in areas where they overlap. The combined dosage values are then stored within the data structure, representing a single layer for electron beam writing.
3. The method of claim 1 , in which creating the data structure comprises: conceptually separating the first virtual layer and the second virtual layer so that the first and second virtual layers are applied sequentially.
Building upon the method for electron beam writing and error correction, the process of creating the data structure involves keeping the virtual layers conceptually separate. Instead of merging the layers, the system treats them as distinct entities to be applied sequentially. This approach allows for applying corrections in a layered fashion during the electron beam writing process, where each virtual layer corresponds to a separate writing pass with potentially different parameters.
4. The method of claim 1 , further comprising: writing the design to the material by loading the saved data structure to an electron beam writing machine.
Expanding on the method of electron beam writing and error correction, the method includes physically writing the design onto a material. This is done by loading the saved data structure into an electron beam writing machine, which then uses the information within the data structure to control the electron beam and create the desired pattern on the material's surface.
5. The method of claim 4 , in which the material is selected from the list consisting of: a semiconductor wafer; and a photomask.
Within the electron beam writing method, the material onto which the design is written can be either a semiconductor wafer (the base material for computer chips) or a photomask (used in photolithography to transfer patterns onto wafers). The electron beam writing process is used to create the fine details of circuits and other structures on these materials.
6. The method of claim 4 , in which writing the design comprises: reading the data structure from the non-transitory computer-readable medium; and applying the first dosage and the second dosage with an electron beam to the material, according to data in the data structure.
In the electron beam writing method that utilizes the data structure, the step of writing the design involves reading the data structure from the computer-readable medium. The electron beam machine then applies the dosage values specified in the data structure to the material, controlling the electron beam intensity and position to create the desired pattern based on the shape and dosage information contained within the data structure.
7. The method of claim 4 , in which applying the first and second dosages includes at least one of: modulating an intensity of an the electron beam; and modulating a speed of writing with the electron beam.
When using electron beams to apply the dosage values specified in the data structure, the electron beam's intensity can be modulated (changed). Alternatively, or in addition to intensity modulation, the speed at which the electron beam writes can also be modulated. Modulating these parameters adjusts the amount of energy delivered to the material at different locations.
8. The method of claim 1 , further comprising the following actions performed before assigning the first dosage to the first polygonal shape: simulating a second write operation on a candidate shape; discerning an error from the second write operation; performing a shape correction operation on the candidate shape in response to the error from the second write operation; simulating a third write operation on a corrected shape; discerning an error from the third write operation; and generating the first polygonal shape to correct the error from the third write operation.
Before assigning the initial dosage value to the first polygonal shape, the process can include these steps: First, simulate writing a candidate shape. Detect any errors. Correct the shape based on those errors. Simulate writing again with the corrected shape. Detect new errors. Generate the final polygonal shape, where the dosage is assigned to correct the errors.
9. The method of claim 1 , in which the first virtual layer and the second virtual layer include at least one of: freedom as to number of polygons; freedom as to dosage; freedom as to shapes of polygons; and freedom as to positions of polygons.
In the method of electron beam writing and error correction, the virtual layers (first and second) offer flexibility in several ways. There are no restrictions on the number of polygons in each layer, the dosage assigned to each polygon, the shapes of the polygons themselves, or the positions of the polygons. This allows for very fine-grained control over the electron beam writing process.
10. The method of claim 1 , in which at least one of the first dosage and the second dosage is negative.
In the electron beam writing method, at least one of the assigned dosage values (either the first or second) can be negative. Using negative dosage is a way to reduce the amount of material deposited or etched away in specific areas, allowing for more complex pattern designs during the writing process.
11. The method of claim 1 , in which discerning an error in the simulated first write operation comprises: comparing a contour of the design in the simulated first write operation to a plurality of target points, the plurality of target points representing an acceptable design shape; and applying a cost function to results of the comparing to quantify the error.
When identifying errors in the simulation of the electron beam writing process, the method compares the contour (outline) of the written shape to a set of desired target points. These target points represent the acceptable shape of the design. A cost function is then applied to the comparison results, which is a mathematical formula to calculate an error.
12. A computer-based system for facilitating electron beam writing, the system comprising: a dosage modulation module for proximity effect correction, the dosage modulation module performing the following functions: create a plurality of polygons, each polygon having a respective dose applied to a respective set of pixels, and further each polygon occupying a respective virtual layer; iteratively apply ones of the layers to correct a simulation writing error; and save the applied ones of the layers to a data structure; and a non-transitory computer-readable medium storing the data structure.
A computer system helps with electron beam writing by correcting proximity effects. A dosage modulation module creates multiple polygons, applying a dose to each polygon's pixels and placing them on separate virtual layers. It adjusts these layers to fix simulation writing errors. Finally, it saves these layers and their settings into a data structure, stored on a computer-readable medium.
13. The system of claim 12 , further comprising: a writing module comprising an electron beam emitter controlled by a processor to write a design from data in the data structure onto a physical material.
The electron beam writing system also includes a writing module that controls an electron beam emitter. A processor uses the data structure (containing information about polygon shapes, dosage values, and layer configurations) to control the electron beam and write the design onto a physical material. The system essentially translates the data structure into precise movements and intensity adjustments of the electron beam.
14. The system of claim 12 , in which the dosage modulation module receives input from a user to select a mode for the data structure, the mode including at least one of: a first mode in which respective virtual layers are conceptually separate; and a second mode in which respective virtual layers are merged.
The dosage modulation module in the electron beam writing system lets users choose how the data structure is organized. One option is to keep each virtual layer separate. Another option is to merge the layers, combining dosage values in overlapping regions. Users can select the mode that best suits their specific design and writing process.
15. A non-transitory computer readable medium tangibly recording executable instructions for performing proximity effect correction, the non-transitory computer readable medium comprising: code to perform a first write simulation operation of a first shape; code to calculate an error for the first shape; code to apply a first polygon in a first virtual layer to the first shape, wherein the first virtual layer overlays the first shape, the polygon defining a first set of pixels with a first dosage, the first polygon generated to address the error; code to create a data structure that includes the first shape and the first virtual layer; and code to output the data structure in a computer-readable file.
A computer-readable storage medium holds instructions for electron beam proximity effect correction. The instructions tell the computer to simulate writing a shape, then calculate the writing error. To fix the error, the computer applies a polygon (with dosage and pixel data) to a virtual layer that overlays the shape. The instructions then create a data structure containing both the initial shape and the applied virtual layer and then output the data structure into a computer-readable file.
16. The non-transitory computer readable medium of claim 15 , in which the code to calculate an error comprises: code to generate a contour from the first write simulation operation; and code to compare the contour to a set of target points representing a desired shape.
The process of calculating the error during the simulation creates a contour (outline) of the written shape. This contour is compared to a set of predefined target points representing the ideal shape. The degree of deviation between the contour and the target points determines the amount of error that needs to be corrected.
17. The non-transitory computer readable medium of claim 16 , further comprising: code to apply a cost function to calculate the error based on results from the code to compare the contour.
Building upon the error calculation of the simulated writing process, the difference between the contour and the target points is fed into a cost function. A cost function assigns a numerical value that represents the magnitude of error; the greater the value, the larger the error. This quantified error is then used to determine how to fix the error.
18. The non-transitory computer readable medium of claim 15 , further comprising: code to calculate a subsequent error present after application of the first polygon to the first shape; and code to generate one or more subsequent polygons to reduce the subsequent error.
After a first polygon is applied to the initial shape for error correction, the system recalculates whether the error is gone or is within acceptable tolerance. If error remains, the system generates one or more additional polygons. These polygons are designed to further reduce the remaining error.
19. The non-transitory computer readable medium of claim 18 , further comprising: saving the one or more subsequent polygons to the data structure.
Following the iterative correction process, the polygons generated to address subsequent errors are saved to the same data structure as the initial correction polygon. This ensures that all corrections are stored together for use by the electron beam writing machine.
20. The non-transitory computer readable medium of claim 15 , further comprising: code to control an electron beam writing machine to write a design to a physical medium by loading data in the data structure to the electron beam writing machine.
The system provides instructions to control an electron beam writing machine. The machine reads the data structure, interprets the polygon and dosage information, and writes the design onto a physical material.
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January 21, 2011
June 11, 2013
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